[x] The Prefects.
[x] Lord and Lady Black
why?Zero'ing immediately on the prefects because being in their good graces could change things significantly for Shinji. Prefects have a lot of power for a young wizard. They can cover for you if you break curfew, take away points from those who annoy you (in case people were worried about House bullying), distribute punishment on some specific individuals (while let you scoff free).
Heck, they could show you the ropes around the school. Remember how beneficial was Hilliard had been to Shinji. They are an absolute need for us, imo. More important than Draco or Amber now, who will bask in their fame and charisma respectively.
Let those who attract attention just shine, we're the one who acts behind the curtain.
Scoring favor points is difficult enough with Severus, especially if you don't approach him yourself. Him being there with his wife is the perfect opportunity for that. Severus is the guy who managed to fool Voldemort with his Occlumency and is super good at Legilimency.
He's also one of the few professors who can understand ambition, since he was once a lone and poor boy who hated his drunk dad himself. Also introvert build tells me he is the guy we should turn to fix issues in the house, rather than Slughorn.
And of course, his children, two natural legilimens would not be a waste to know, should you look for extra help for your training.
Well, that's the logic behind the choices, anyway.